(a) Field of the Invention
This invention relates to a ventilating needle required for application to a liquid or blood transfusing system or a connector assembly and, also to the method of manufacturing said ventilating needle.
(b) Description of the Prior Art
Referring to a liquid or blood transfusing system or a connector assembly, the withdrawal of a medical solution, for example, from a bottle, has hitherto been carried out by piercing a ventilating needle through the stopper of the medical solution bottle and introducing air streams into the medical solution bottle through said ventilating needle. In this case, the ventilating needle is generally fitted with a filter in order to prevent dust and other foreign matter from entering said ventilating needle from the outside. The various processes proposed to date to meet this requirement involve a means of forcing a rounded mass of fine fibers like those of, for example, purified cotton into the hub section of the ventilating needle, or embedding a sintered mass of for example, polyethylene in said hub section. This is the so-called depth type filter. The second main process is the so-called screen type filter disclosed, for example, in the Utility Model Publication No. 58-92946 which is constructed by fixing a filter composed of, for example, a membrane to the hub section of the ventilating needle by means of a cap or holder.
The depth type filter has drawbacks in that it tends to have dense and loose sections, it is insufficiently resistant to hydraulic pressure, it is unsatisfactory in terms of ventilation, and it is insufficiently able to remove bacteria.
The screen type filter has merits in that the ventilation pores can have a relatively uniform size, which permit better waterproofing and ventilating. Nevertheless, said screen type filter has drawbacks in that it is fitted to an extra member such as a cap or inserted into the needle hub section by means of a holder; air contaminated with dust and other foreign matter can pass between the filter and the hub. This makes the ventilating needle complex in structure, relatively difficult to assemble, and expensive.